THE LIFE OF MAMMALS 
remaining only as a splint) and the middle toe so prominent 
that the hinder toes did not touch the ground, as in the case 
of the ‘false hoofs” of deer or cattle. The toes disappear 
as they are least used, so that the thumb would be the first to 
EVOLUTION OF THE SINGLE-TOED EQUINE FOOT. 
Diagram (after Osborn) illustrating by means of the human hand the process of gradual 
loss of side toes by concentration of weight and service upon the middle digit. 
go, as Osborn showed the reader could illustrate for himsclf 
by placing his fingers in a faotlike position. 
““We may imagine,” writes Osborn, ‘‘the earliest herds of 
horses in the Lower Eocene (Eohippus) as resembling a lot 
sheidnetiy at of small fox terriers in size, . . . covered with short 
Horse. § hair which may have had a brownish color with 
lighter spots, resembling the sunbeams falling through the leaves 
of trees, and thus protecting the little animals from observation. ”’ 
Mesohippus was succeeded in the Miocene by Parahippus, 
and also by Protohippus in the Upper Miocene, the latter of 
which was somewhat larger, showed an increasing centraliza- 
tion of weight on the middle toe, and had teeth a little more 
advanced toward the modern pattern from the early short and 
tubercle-crowned type. At this date, also, several other forms 
existed both in Europe and in North America, which proved 
to be aside from the direct line of evolution, and whose races 
soon died out. Among them was the American ‘‘forest horse” 
(Hypohippus), described by Osborn as ten hands high, with 
large lateral toes serving to keep the feet from sinking into the 
relatively soft ground of the warm forest sand lowlands of its 
day, where it sought the softer kinds of herbaceous food for 
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